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Vineyard Cover Crop Management in the North Willamette Valley
Jessica Howe Sandrock and Anita Nina Azarenko Depm1ment of Hm1iculture, Oregon State University Industry Collaborators Allen Holstien, Stoller Vineyards and Domaine Drouhin Oregon Leigh Bm1holomew, Archery Summit Vineyards Funding provided by the Oregon Wine Board Introduction The objectives of this study are to determine: o How vine vigor and fmit composition vary in different alleyway management regimes:
solid vegetative cover vs. every other alleyway of vegetative cover removed
o What differences are observed in different alleyway management regimes within a
vineyard
o What differences are observed in different alleyway management regimes between
vineyards with similar soil type
The first year of this study (2006 growing season) is intended to focus on achieving baseline data
for all sites.
Justification of Research
Vineyard alleyway management is an impot1ant aspect of growing healthy grapevines and
producing high quality fruit. Each vineyard is unique in terms of how alleyways should be
managed in order to achieve a specific goal. Soil type, slope, vine density, and water availability
should be considered when making decisions about how to manage vineyard alleyways (5).
Vineyards located in the Nmih Willamette Valley of Oregon experience an average annual
rainfall of 40" (4). Most of this rainfall occurs between October and June. Available Water
Holding Capacity of the soils in this area range from 6.5-10.3 inches (1 ). A challenge that grape
growers face in the Nm1h Willamette Valley is to manage relatively high amounts of available
water in the spring and potentially low amounts of available water in the summer during fruit
ripening. Strategically managing the vegetative cover to influence water availability and the
implementation of irrigation are two tools that Willamette Valley Growers have used to deal with
this challenge.
When vegetative cover is actively growing it is competing for water and nutrients with the
grapevine (2,3). This can be advantageous in a vineyard that receives high winter rainfall on soils
with high water holding capacity. Early season water competition can help grow a smaller, less
vigorous, canopy (5) that is easier and less expensive to manage. Growing a smaller canopy can
also reduce shading and disease pressure which will result in higher fmit quality.
If a grower's goal is to reduce water and nutrient competition, vegetative cover can be removed
in early spring. Typically this has been done by tilling the cover in when soil conditions and
equipment availability allow. Tilling the cover in will reduce competition while adding biomass
to the soil (2,5). The thought being that nitrogen is being put back into the vineyard system for
the vine to use later (3).
It is known that grapevines use plant nitrogen reserves for growth from bud break until bloom.
Grapevines stm1 to use soil available nitrogen when 5-7 leaves have expanded until fruit set. The
maximum amount of soil available nitrogen uptake occurs at fruit set. After fruit set the use of
soil available nitrogen declines and redistribution of nitrogen that has accumulated in the vine
canopy is used during stage three offruit ripening. Translocation of nitrogen from the canopy
continues until leaf senescence. There is a brief period after harvest and prior to leaf senescence
that soil available nitrogen can be taken up if conditions allow (6).
Managing alleyways to manipulate vine growth and physiology is a matter of timing and
intensity. It is the goal of this study to consider the degree to which competition from vegetative
cover is beneficial in commercial vineyards in the North Willamette Valley and eventually
consider the best times to impose or remove competition.
Materials and Methods
Experimental Design
This experiment is being conducted in three commercial vineyards located in the North
Willamette Valley: Stoller Vineyard, Archery Summit, and Domaine Drouhin Oregon
(DDO). Table 1 describes site details for all three vineyards.
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Vineyard Details
Table I· Site details for Stoller Vineyard Archery Summit Vineyard and DDO
'
'
Stoller
Archery Summit
DDO
alternate row removal alternate row removal alternate row removal
Treatment
of cover crop (EO) vs. of cover crop (EO) vs. of cover crop (EO) vs.
comparisons
solid cover crop (S)
solid cover crop (S)
solid cover crop (S)
vs. complete cover
crop removal (CR)
Treatment
Complete randomized Complete randomized Complete randomized
organization
block design
block design
block design
Treatment
Replicated five times
Replicated five times
Replicated three times
replication
on groups of 16 vines on groups of24 vines on groups of 16 vines
Perennial blend
Cover crop
Mix of reemerging
Perennial grass plus
composition
red fescue (seeded
(Bailey Seed Pathway volunteer species
2002) and Kentucky
Blend)of 60% Elf
(seeded fall 2005)
bluegrass (seeded
perennial rye grass,
Sept. 2005)
20% creeping red
fescue, 20% hard
fescue (seeded winter
2006 in clean
cultivated rows from
2005)
Cover removed for
April 19, 2006
April 19,2006
May 81", 2006
Alternate (EO) and
Complete (CR)
treatments
spaded
tilled
How cover was
tilled
removed
no
no
yes
Irrigation
Pommard/Riparia
667/101-14
Pommard/3309
Plant material
1996
1989
Year planted
1999
1
April
26'", 2006
April
19,
2006
April15
\
2006
Budbreal<
Parameters of Interest
Vegetative vigor- Pruning weights were collected per vine on December i\ 2006 at
Stoller and DDO. Pruning weights were determined by weighing all of the one-year old
wood per vine.
Shoot count- The number of shoots per vine were determined post-harvest at Stoller and
DDO.
Ripening dynamics- Brix, pH, and T A were monitored during ripening. Sampling began
at the onset ofveraison and occurred on a weekly basis until harvest. 5 clusters per
replicate were collected in the morning and processed immediately. Soluble solids (brix)
ofjuice samples were determined using a hand held refractometer. pH ofjuice samples
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was determined using a Scholar 425 pH meter and Sentix 62 electrode. Titratable acidity
was determined using the titrametric procedure using NaOH as described by Zoecklein et
a! (7).
Fruit composition at harvest- Each treatment replicate was harvested separately. 25
clusters per replicate were collected in the morning and processed immediately. Must
samples were delivered to ETS Laboratories (McMinnville) for analysis. Basic juice
profile was determined using ETS Laboratories methods for brix, pH, titratable acidiy, L­
malic acid, tartaric acid, potassium, glucose and fi·uctose, alpha-amino compounds, and
ammonia.
The affects of cover crop management on vine vigor and fruit composition were analyzed using
the ANOV A procedure and subjected to the t-test. All statistics were performed using the SAS
System version 9 statistical package.
Results
The experimental block at Archery Summit was lost following fruit set. Therefore, no results
were obtained fi·om that site. Fruit from the DDO site was lost at harvest. Therefore, fruit
composition at harvest was not evaluated.
Stoller
Ripening dynamics -No treatment differences were observed in juice soluble solids, pH, or
titratable acidity (TA) during ripening or at harvest (Figure !a, Figure 1b, and Figure !c). The
alternate row (EO) treatment tended to have higher brix during the last three weeks of ripening
(Figure !a). The increase in brix, for both treatments, between September 20'" and harvest
(September 29'") may be due to precipitation that occurred during this week followed by high
temperatures. Beny dehydration may have occurred. A similar increase in pH was observed in
both treatments (Figure 1b).
Fruit composition at harvest- Malic acid and alpha-amino compounds were significantly higher
in the solid cover treatment (S) at harvest (Table 2). The literature suggests that reducing
vegetative competition may enable vines to translocate nitrogen stored in the canopy to the fruit
during ripening (3). These results do not supp01i that theory. This suggests that the solid cover
treatment did not have a negative affect on nitrogen accumulation in the fruit prior to harvest.
This may be due to the fact that this vineyard site is irrigated and vines were able to continue
translocation regardless of vegetative competition.
Vine vigor- Table 3 and Table 4 illustrate vine vigor in 2005 and 2006 respectively. Pmning
weights decreased in both treatments in 2006 (Table 4). There was a greater decrease in vigor in
the solid cover treatment (S) between 2005 and 2006. This suggests that regardless of this site
being irrigated these vines may have undergone greater competition for resources than the
alternate row treatment (EO).
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DDO
Ripening dynamics - On one date during ripening (Figure 2a) the solid cover treatment (S) had
significantly higher brix than the alternate row (EO) or complete removal treatment (CR). On the
final sampling date prior to harvest, no treatment differences in brix were observed. Treatment
differences in titratable acidity were observed on September 61h and September l3 1h (Figure 2c)
with the alternate row treatment (EO) having higher TA on both dates. The complete removal
treatment (CR) also had higher TA than the solid cover treatment (S) on September 13 1h. No
treatment differences were observed in pH (Figure 2b).
Vine vigor- Table 5 and Table 6 illustrate vine vigor in 2005 and 2006 respectively. No
treatment differences were observed and vigor tended to decrease in all treatments between 2005
and 2006.
Summary and Future Wo1·k
Results from the first year of this study suggest that manipulating vegetative competition in the
alleyway can manipulate vine vigor and the vines ability to translocate material from the canopy
to the fruit during ripening. However, imposed vegetative competition can possibly be overcome
by irrigation.
Future work on this project will seek to improve experimental design by adding a complete cover
removal treatment to serve as a control at all three sites. Additional canopy density data will be
evaluated during the growing season. Collaborators and other industry patiicipants have also
determined that additional fruit and wine composition parameters need to be evaluated.
Specifically, aroma and flavor precursors in the fruit and wine will be evaluated. Future
collaboration with The Department of Food Science and Technology, OSU, will address these
new research questions in 2007.
Figure 1: Juice soluble solids (a), pH (b), and titratable acidity (c) of juice during ripening
and at harvest at Stoller Vineyard (2006). *,**,and*** indicate statistically significant at
the 0.05, 0.01, and 0.001levels of probability, respectively.
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Figure 2: Juice soluble solids (a), pH (b), and titratable acidity (c) of juice during ripening
at DDO Vineyard (2006). *,**,and*** indicate statistically significant at the 0.05, 0.01,
and O.OOllevels of probability, respectively.
-+-Sofid (S) ----Alternate Cover (EO) __,_Complete Removal (CR) 24
*
w
:2
0
"'.c-"
20
"'•
..,"
18
0"
.~
16
''';/L
~
.
,:
14
24-Aug
31-Aug
14-Sep
21-Sep
--~-·-
-·-----,1
b3.30
--+-So!id(S) --Alternate Cover (EO) -~<--Complete Removal (CR) 3.25
3.20
3.15
3.10
:I:
Q,
•
..,"'"
3.05
3.00
2.95
2.90
2.80 +-----~---~----~----,.--"
24-Aug
31-Aug
7-Sep
c
16-,---­
-+--Sofld(S) ---Alternate Cover (EO) --Complete Removal (CR) 6
4+----~----,-----~---~
24-Aug
31-Aug
14-Sep
21-Sep
Table 2 · Basic juice profile means of Stoller Vineyard at Harvest (September 29 , 2006)
Solid Cover
Alternate Cover
Significance
(S)
(pvalue)
(EO)
brix (0 )
26.1
25.9
ns
(0.6817)
pH
3.43
3.38
ns
(0.0618)
titratable acidity
0.61
0.57
ns
(g/100ml)
(0.2461)
potassium (mg/L)
1022
964
L-malic acid (g/L)
3.06
2.40
tartaric acid (g/L)
4.52
4.81
glucose + fructose
(g/100ml)
28.76
28.34
alpha-amino
compounds (mg/L)
232.20
190.00
ammonia (mg/L)
ns
(0.1717)
*
(0.0470)
ns
(0.0601)
ns
(0.4992)
*
(0.0348)
180.0
ns
(0.1260)
..
.
. ' ' md1cate
ns, ~, n, and ~n
not s1gmficant, and statistically s1gmficant at the 0.05, 0.01, and 0.001
levels of probability, respectively.
Table 3: Vine vigor at Stoller Vineyard (2005)
Solid Cover
(S)
2.27
pruning weight
(i<g/vine) 21
shoots per vine
pruning weight per
shoot (g) ..
...
I 07.39
159.6
Alternate Cover
(EO)
2.33
21
112.19
Significance
(pvalue)
ns (0.7039)
ns
(0.7632)
ns (0.4343)
ns, ~, n , and h~ md1cate not s1gmficant, and statistically s1gmficant at the 0.05, 0.01, and 0.001
levels of probability, respectively.
Table 4· Vine vigor at Stoller Vineyard (2006)
Solid Cover
(S)
1.47
pruning weight
(kg/vine)
20
shoots per vine
pruning weight per
shoot (g)
Alternate Cover
(EO)
1.76
Significance
(pvalue)
*
(0.0415)
ns
(0.5684)
ns
(0.0956)
20
73.66
86.35
''' .
ns, ~,""",and~"""
md1cate not s1gmficant, and statistically s1gmficant at the 0.05, 0.01, and 0.001
levels of probability, respectively.
0
0
Table 5· Vine vigor at DDO Vineyard (2005)
Alternate Cover
Solid Cover
(S)
(EO)
0.61
0.60
pruning weight
(kg/vine)
9
9
shoots per vine
68.03
pruning weight
per shoot (g)
69.35
Complete
Removal (CR)
0.59
9
65.30
Significance
(pvalue)
ns
(0.7865)
ns
(0.0775)
ns
(0.3795)
ns, "',"'*,and •~• md1cate not s1gmficant, and statistically s1gmficant at the 0.05, 0.01, and 0.001
levels of probability, respectively.
Table 6· Vine vigor at DDO Vineyard (2006)
Solid Cover
Alternate Cover
(S)
(EO)
0.58
0.60
pruning weight
(kg/vin~)
10
10
shoots per vine
61.96
pruning weight
per shoot (g)
59.92
Complete
Removal (CR)
0.59
10
60.88
Significance
(pvalue)
ns
(0.7651)
ns
(0.5062)
ns
(0.8952)
ns, "',""",and ~•• mdJCate not s1gmficant, and statlstJCal!y s1gmficant at the 0.05, 0.01, and 0.001
levels of probability, respectively.
0
0
0
0
Acknowledgements
Financial support for this project provided by the Oregon Wine Board is greatly appreciated as is
the technical support from ETS laboratories and the collaboration and commitment from Stoller
Vineyard, Domaine Drouhin Oregon, and Archery Summit Vineyard.
References Cited
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performance. CSIRO Land and Water Technical Repm1 No. 34/04.
3. Rupp, D. (1996). Green cover management to optimize the nitrogen supply of grapevines.
Proc.Workshop Strategies to Optimize Wine Grape Quality. Acta Hort. 427:57-62.
4. Western Regional Climate Center. http://www.wrcc.dri.edu/pcpn/or.gif
5. William R.D. and D. Crisp (2003) Floor Management. In E.W. Hellman (Ed). Oregon
Viticulture (pp. 167-171). Corvallis, OR: Oregon State University Press.
6. Winkler, A.J., J.A. Cook, W.M. Kliewer, and L.A. Lider (1962). General Viticulture (2 11d Ed).
CA: University of California Press.
7. Zoecklein B.W., K.C. Fugelsang, B.H. Gump, and F.S. Nury (1999). Wine Analysis and
Production (pp. 511 ). Gaithersburg, Maryland: Aspen Publication.